1. Field of the Invention
This invention relates, generally, to machines that insert sheets of paper or other items into envelopes. More particularly, it relates to a feeder machine that operates at a very high speed.
2. Description of the Prior Art
Machines for inserting items such as sheets of paper into envelopes at a relatively high rate of speed have been known since the 1930s. They can perform about 8000 insertions per hour when properly maintained and adjusted. At least thirty six patents cover the original machine and various improvements thereto.
The known machine is mechanically complex. For example, it employs a total of nine cams for performing various functions such as opening and closing mechanical clamping devices, raising and lowering suction cups used for opening envelopes, and so on. It includes a large number of gears, belts, drive shafts and the like. There are so many mechanical complexities that the device even includes a unique device for taking looseness or play out of the mechanism. The mechanical complexity relies upon human oversight for frequent adjustment purposes but even a well-adjusted machine is subject to frequent paper jams and the downtimes associated therewith.
Moreover, the envelope feeder of the known machine holds only a short stack of envelopes. As a result, the machine operator must frequently replenish the stack. A taller stack is contraindicated because the mechanism must remove envelopes sequentially from the bottom of the stack. The mechanism cannot cope with the extra weight of a tall stack, or the changing weight of a stack that steadily decreases in height as the machine operates.
The earlier machine also includes a reciprocating, pivotally-mounted, pendulum-like arm that feeds each sheet of paper or small stack of sheets into each envelope. It swings forwardly to perform one insertion and then swings back to prepare for the next insertion. This back-and-forth cycle takes place eight thousand times an hour when the machine is operating smoothly. Since the arm has non-negligible mass, the need to change direction sixteen thousand times per hour places a strain on the machine and prevents faster operation.
Another limitation of the known machine that restricts it to 8000 insertions per hour is conveyor speed. If the conveyor that delivers the sheets to the envelopes is run any faster than its 8000 insertions per hour speed, the envelopes into which the sheets are to be inserted cannot be delivered to the insertion station quickly enough. Moreover, the increase in speed of the conveyor belt causes the sheets to fly from it.
Another source of the known machine's relatively slow speed of operation is the use of suction cups to open envelopes at the sheet insertion station. Since suction cups cannot grasp a moving envelope, each envelope must come to a full stop before the suction cups can be lowered into engaging relation thereto. After the sheets have been inserted, the suction cups must be released and moved upwardly again so that the cycle can be repeated for the next envelope.
The known machines are further limited because the envelopes and sheets to be inserted thereinto follow a parallel path of travel as they approach a sheet insertion station. This requires that rectangular sheets be inserted in a "narrow edge leading" position, i.e., the sheets are pushed into the envelope in their long dimension. This requires a time delay for indexing to occur and an acceleration of the paper thereafter to make up for the delay.
The known machines also incorporate flighted conveyor belts, in their collator section, where longitudinally spaced apart vertical walls divide the belt into bins of ten inches in length. If bins of different lengths are needed for a particular application, a different belt must be installed.
What is needed, then is a machine that can perform insertions at a rate of speed much faster than eight thousand insertions per hour.
There is a need as well for a machine with less mechanical complexity. A more elegantly-designed machine could operate at higher speeds with increased reliability and less downtime, and would require less operator attention.
A need also exists for an envelope feeder that does not require frequent replenishment.
Another need exists for a machine that does not rely upon a pivotally-mounted, reciprocating arm to push paper sheets into envelopes.
Moreover, there is a need for a machine that can deliver more sheets per hour without increasing the speed of the conveyor belt that delivers the sheets to an envelope insertion station.
There is a need as well for an improved means for opening envelopes prior to sheet insertion. The improved means should not require the envelope to reach a full stop before the insertion procedure begins and the improved means should not rely upon suction cups.
A need exists as well for a machine that can feed sheets of rectangular paper in a "wide edge leading" format so that the short side of a rectangular sheet is pushed into its envelope, thereby reducing the length of each pusher stroke and eliminating a need to index, delay and accelerate the mechanisms involved in the sheet insertion process.
A need is extant, further, for a machine having a flighted conveyor belt in its collator section that is not limited to ten inch bins and which can be modified to have bins of differing length without requiring changing of the belt.
However, it was not obvious to those of ordinary skill in this art how the needed improvements could be provided, in view of the art considered as a whole at the time the present invention was made.